Ethanol derived from renewable feedstock has the potential to meet one of the greatest challenges to today's society as a sustainable replacement of fossil fuels, especially in the transport sector, with reduction in greenhouse gas emission. In 2005, a record of 15.1 billion liters (4 billion gallons) of fuel ethanol was produced in the U.S. There are currently 109 ethanol plants in operation with the capacity of 19.8 billion liters (5.2 billion gallons), and 53 plants under construction will increase the capacity to 35.7 billion liters (9.4 billion gallons) (December 2006 Data). In the U.S., corn is the primary feedstock for fuel ethanol production and for example, in 2006, about 20% of the U.S. corn supply was used to make fuel ethanol to replace only 3-4% of the gasoline supply. In order to avoid the “fuel versus food” issue, an alternative to corn feedstock is needed. Among others, barley has great potential as an alternative feedstock for ethanol production, especially in the Mid-Atlantic and other states, where it is a winter crop, allowing double cropping with soybean. It is estimated that in North America, barley can provide at least one billion gallons of ethanol per year, which is about 20% of the total ethanol production in the U.S. in 2006.
However, there is no plant in the U.S. using barley as a feedstock since regular hulled barley can not be processed in a conventional corn-to-ethanol plant without modifications due to the following reasons: 1) the abrasive nature of hulled barley would damage grain handling and grinding equipment, thus increasing capital costs, 2) the low starch content (50-55%) of barley would result in lower ethanol yield compared to corn requiring barley plants to be built larger than corn plants for the same capacity, 3) the high viscosity of barley mashes due to beta-glucan, and 4) the production of a distillers dried grains with solubles (DDGS) co-product with high levels of beta-glucan that can't be used for poultry, swine, and aquaculture feeds, which limits the value of the co-product in poultry and swine production areas.
In order for a barley-to-fuel-ethanol process to be economically successful, the abovementioned technical hurdles must be overcome. The objective of this paper is to develop a barley-based STARGEN™ process for ethanol production.